The present invention relates to a connecting structure for an oscillator for use with a simplex type mobile radio communication equipment, for example.
In the simplex type radio communication equipment, transmitting and receiving are not carried out simultaneously, but they are selected to be independently operated. FIG. 3 shows a circuit diagram of the simplex type radio communication equipment. In transmitting, a carrier formed by a carrier oscillator 22 is modulated by a sound signal from a microphone 21, and is amplified by an amplifier 23. Then, it is fed through a band pass filter 24 and an output amplifier 25 to an antenna switch 26, and is transmitted from an antenna 27. In receiving, the antenna switch 26 is selected to a receiving position, and an input signal from the antenna 27 is fed to a mixer 28. On the other hand, an output from a local oscillator 29 is fed through the amplifier 23 and a band pass filter 30 to the mixer 28. Then, it is mixed with the input signal from the antenna 27 in the mixer 28 to obtain an intermediate frequency. In this circuit, a pair of oscillators (the carrier oscillator 22 and the local oscillator 29) are both connected to the amplifier 23, and either of the output from the oscillator 22 or the output from the oscillator 29 is input to the amplifier 23.
FIGS. 4 and 5 show an exemplary connecting structure for the oscillator as mentioned above. The oscillators 22 and 29 are mounted on a substrate 31 above the upper surface of a shield plate 37 made of metal, and the amplifier 23 is mounted on a substrate 32 below the lower surface of the shield plate 37. The oscillators 22 and 29 are formed from a pair of resonators 36 each including a cylindrical dielectric 33, an inner conductor 34 and an outer conductor 35 as electrodes both attached to the cylindrical dielectric 33, and from an oscillator circuit including a pair of oscillator circuit parts 38 mounted on the substrate 31 fixed to the shield plate 37 at its one end by an adhesive or the like. Each resonator 36 is fixed to the shield plate 37 by directly soldering the outer conductor 35 to the shield plate 37. On the other hand, the amplifier 23 includes a pair of amplifier circuit parts 39 mounted on the lower surface of the substrate 32 fixed to the lower surface of the shield plate 37. The substrates 31 and 32 and the shield plate 37 are formed with a through-hole 40 for inserting a connecting rod 41 thereinto. The connecting rod 41 is soldered at its upper and lower ends to the substrates 31 and 32, thereby electrically connecting the oscillator circuit with the amplifier circuit. With this arrangement, the oscillation generated from the resonators 36 is intended not to have an influence upon the amplifier circuit.
However, the prior art structure as mentioned above is a three-layer structure constructed of the pair of substrates and the shield plate. This three-layer structure causes the following disadvantages.
(1) The number of parts is increased to cause an increase in material cost.
(2) The number of manufacturing steps is increased to cause an increase in manufacturing cost.
(3) In receipt of external mechanical vibration, each substrate and the shield plate are independently vibrated to cause a reduction in S/N ratio.